1. Field of the Invention
The present invention relates to a method of and apparatus for removing contaminants, such as particles and organic material, from a semiconductor substrate or a liquid crystal display (LCD) substrate.
2. Description of the Related Art
In the process of manufacturing an integrated circuit (IC), such as a memory device or an LCD, the surface of a substrate of the IC may be contaminated. Contaminants on the surface of a substrate may include organic material, dust, residue, and metal contaminants. Such contaminants may be divided into two types: organic materials that can be removed mainly by a chemical reaction and particles that can be removed mainly by physical force. This contamination typically occurs when the substrate is being stored or is in a stand-by state between successive processes. The contaminants may create defects that ultimately cause the integrated circuits to malfunction. For example, organic residue on the surface of a substrate may cause a defect in a subsequently formed thin film or may increase the contact resistance of the device.
Thus, a step of cleaning the surface of a substrate, such as a wafer, is attendant to each process performed in the manufacturing of an integrated circuit such as memory device or an LCD. The cleaning is performed to remove organic contaminants or contaminant particles from the surface of the substrate. Conventional wet cleaning techniques have been used for cleaning the surface of a substrate. It is well-known that these wet cleaning techniques are very effective in removing contaminant particles from the surface of a substrate. Furthermore, the wet cleaning techniques include the use of a spin brush during cleaning or an ultrasonic or megasonic cleaner to enhance the cleaning effect.
Despite the significant efforts directed towards cleaning the surface of a substrate, the effectiveness of conventional wet cleaning techniques is quite limited when the circuit patterns of the memory device or LCD are extremely fine. For example, the use of a spin brush or an ultrasonic cleaner may damage the fine patterns of a memory device or an LCD. Furthermore, although a spin brush or an ultrasonic cleaner in a wet cleaning process may be effective in removing large contaminant particles, they are hardly effective in removing particles on the order of submicrons.
Furthermore, along with the miniaturization of the patterns, there is a trend in which a gate or a bit line includes metal such as tungsten (W). Many conventional wet cleaning processes would be detrimental to the metal. Therefore, wet cleaning a substrate on which such a gate or bit line has been formed is limited to rinsing the substrate with deionized water or a minimal cleaning using a stripper. In these cases, it becomes increasingly difficult with any reliable degree to effectively prevent a defect from occurring during a fabrication process.
Recently, a number of new cleaning techniques have been developed for removing contaminants such as particles or organic residue. For example, according to one approach, an aerosol including microscopic frozen particles is sprayed over the surface of a substrate to remove contaminants from the surface of the substrate. U.S. Pat. No. 5,967,156 issued on Oct. 19, 1999 to Peter H. Rose et al., and entitled xe2x80x9cProcessing A Surface,xe2x80x9d describes a such a method.
More specifically, the patent discloses a method of removing foreign material (for example, particulate contaminants such as dust and metals, and organic material such as photoresist and fingerprints, and residue) from the surface of a substrate by reacting a reactant gas with the foreign material. An aerosol including frozen particles is applied along with a flow of the reactant to the surface of the substrate to aid the reaction of the reactant gas with the foreign material. The surface of the substrate is irradiated with infrared (IR) or ultraviolet (UV) light to heat the substrate, and thereby further aid the reaction of the reactant gas with the foreign material.
However, the effectiveness of the aerosol in cleaning the surface of the substrate is reduced because both the physical and chemical cleaning processes are performed simultaneously in the same place. More specifically, the ultraviolet or infrared light produced during the chemical cleaning process may reduce the effectiveness of the aerosol because ultraviolet and infrared light are radiant forms of energy. Therefore, the ultraviolet or infrared light is absorbed by the walls of the processing chamber and at the surface of the substrate, in particular, by contaminants on the substrate surface or by the reactant fluid. Furthermore, the ultraviolet or infrared light may also be absorbed by the nozzle from which the aerosol issues. Therefore, the temperature inside the processing chamber may rise so much as to preclude frozen particles from issuing from the nozzle. Even if the frozen particles do issue from the nozzle, there is high possibility that the frozen particles will evaporate before reaching the surface of the substrate. Thus, there are hardly any frozen particles to collide with contaminant particles.
Accordingly, it is highly desirable to provide a method of and apparatus for effectively removing contaminants, such as organic residues or particles, from the surface of a substrate.
An object of the present invention is to solve the above-described problems by providing a method of and apparatus for effectively removing contaminants, including particles and organic material, from the surface of a substrate in the process of fabricating an integrated circuit such as a memory or a liquid crystal display (LCD).
Cleaning apparatuses of the present invention include means by which particles on the surface of a substrate are removed mainly by physical force using an aerosol comprising frozen particles, and means by which organic contaminants are chemically removed in a separate process by a gaseous reactant and radiation providing activation energy for a chemical reaction between the reactant and organic contaminants on the surface of the substrate. That is, in the present invention, a physical cleaning process using frozen particles is performed independently of a chemical cleaning process using a fluid reactant and light so that the activation energy required by the chemical cleaning process does not reduce the effectiveness of the frozen particles used to carry out the physical cleaning process.
According to one aspect of the present invention, the cleaning apparatus includes: a transfer chamber, a first cleaning chamber connected to the transfer chamber, a reactant supplier associated with the first cleaning chamber so as to expose the surface of a substrate to a reactant within the first cleaning chamber, a light source also associated with the first cleaning chamber to irradiate the substrate and thereby supply the activation energy required to cause a chemical reaction between the reactant and contaminants on the surface of the substrate, a second cleaning chamber connected to the transfer chamber, and an aerosol generator associated with the second cleaning chamber for jetting an aerosol containing frozen particles onto the surface of the substrate within the second cleaning chamber.
The light source may be an ultraviolet or infrared lamp that irradiates the substrate within the first cleaning chamber.
In a specific method according to the present invention executed in conjunction with this apparatus, a substrate is transferred from the transfer chamber to one of the cleaning chambers whereupon one of the cleaning processes is performed therein, then the substrate is transferred to the other cleaning chamber via the transfer chamber whereupon the other cleaning process is performed. Accordingly, the infrared or UV light provided by the light source does not affect the efficacy of the frozen gas particles because the light and the frozen gas particles are provided in separate spaces, i.e., the first and second cleaning chambers.
The aerosol generator may be a nozzle disposed above the inlet of the second cleaning chamber for jetting the aerosol onto the surface of the substrate as the substrate enters the second cleaning chamber.
According to another aspect of the present invention, the cleaning apparatus includes: a transfer chamber, a cleaning chamber connected to the transfer chamber, an aerosol-generating nozzle disposed in the cleaning chamber for jetting an aerosol containing frozen particles onto the surface of a substrate transferred into the cleaning chamber, a reactant supplier that exposes the surface of the substrate to a reactant within the cleaning chamber for chemically removing contaminants from the surface of the substrate, and a laser beam generator that directs a laser beam onto the surface of the substrate transferred into the cleaning chamber in order to supply the activation energy required to chemically react the reactant with the contaminants.
The aerosol-generating nozzle and the laser beam generator are oriented so that the aerosol is directed onto a region of the substrate separate from that onto which the laser beam is directed while the substrate is being transferred through (to or from) the cleaning chamber. Accordingly, the laser beam used for chemically cleaning the substrate does not impinge the frozen particles used for physically cleaning the substrate.
In a specific method according to the present invention executed in conjunction with this apparatus, a substrate is transferred from the transfer chamber into the cleaning chamber. As the substrate enters the cleaning chamber, the aerosol is jetted onto a leading region of the substrate surface and is physically cleaned (first cleaning process). The leading region then advances under the laser beam, whereby the activation energy is provided at the leading region so that the leading region is chemically cleaned 9 second cleaning process). The substrate is then withdrawn from the cleaning chamber into the transfer chamber, whereby the leading region again is exposed to the aerosol jet (third cleaning process). In this way the entire substrate surface is both physically and chemically cleaned in a separate manner within the same cleaning chamber.
The cleaning methods thus can effectively remove contaminants, both particles and organic material, from the surface of the substrate during the fabricating of an integrated circuit such as a memory device or an LCD.